Testing aspheric surfaces using multiple annular interferograms

Abstract

We present a technique for interferometrically testing aspheric surfaces without the use of compensating elements. The method consists of recording successive overlapping phase maps from a set of annular interferograms of an aspheric surface, obtained using a conventional phase-shifting interferometer and a micropositioning translator stage. These maps are then sewn together with a suitable algorithm we developed, and the whole surface error is recovered. Experimental results are shown to be in good agreement with the null lens test performed for comparison.